Electrochemical cell including a tubular foraminous partition



Ndv. 22, 1966 D. G. BRAITHWAITE 3,287,248

ELECTROCHEMICAL CELL INCLUDING A TUBULAR FORAMINOUS PARTITI ON FiledAug. 31, 1962 FIG 2 52 FIG! 54 55 26 3 i 3 3 T w 28 23 E 27 I9 7 22 A?ll INVENTOR: DAVID G. BRAITHWAITE 73 M314 Mal-x i ATT 'YS United StatesPatent ELECTROCHEMICAL CELL INCLUDING A TUBULAR FORAMINOUS PARTITIONDavid G. Braithwaite, Chicago, Ill., assignor to Nalco Chemical Company,Chicago, 11]., a corporation of Delaware Filed Aug. 31, 1962, Ser. No.220,699

12 Claims. (Cl. 204-260) This invention relates to a liner or partitionfor an electrolytic cell and more particularly to a foraminous partitionfor location within the annular electrolyzing zone of a cell forelectrolyzing a sacrificial anode in a liquid electrolyte. The inventionis especially concerned with a new and improved tubular electricallynon-conducting liner or partition which is employed in anelectrochemical cell for the manufacture of tetraalkyl lead compounds,including, for example, tetraethyl lead tetramethyl lead,triethylmonomethyl lead, diethyldimethyl lead, monoethyltrimethyl lead,and mixtures thereof, and which is useful in the manufacture of otherorganic metallic compounds by an electrolytic process involving the useof a sacrificial anode.

The term sacrificial anode refers to an anode which is eroded ordissolved during the electrolytic process.

In one type of sacrificial anode process employed for making tetraakyllead compounds, the lead anode is in particulate form, that is,particles, spheres or pellets. The electrolyte is an organic magnesiumcompound, such as a Gringard reagent, dissolved in an anhydrous solventand this is circulated through the lead particles. The cathode consistsof an electrically conducting metal, such as steel and a foraminouspartition, liner or diaphragm is placed between the metal cathode andthe lead particles in such a way that it is in contact with both. Inthis way, the cathode. and the lead particles are very close to eachother and a narrow space between them is provided by the partition. Theelectrolyte circulates through the anode particles and through thenarrow space between these particles and the cathode. It is essentialthat the foraminous partition be electrically non-conducting and thatthe lead particles should be held out of direct contact with the cathodeby the partition. At the same time, it is desirable that the leadparticles and the cathode be as close together as possible and thatthere be a maximum circulation of the electrolyte in the narrow spacebetween them.

The lead particles being heavy exert considerable drag on the partitionwith which they are in contact and it is necessary to provide a verydurable partition which will not sag and in which the openings will notbecome enlarged so as to permit the lead particles to contact thecathode directly and short circuit the cell.

One of the objects of the present invention is to provide a new andimproved type of foraminous partition which is so constructed as tofacilitate passage of a liquid electrolyte between the anode particlesand the cathode.

Another object is to provide a new and improved tubular electricallynon-conducting foraminous partition for location within an annularelectrolyzing zone of a cell for electrolyzing a sacrificial anode in aliquid electrolyte which is so constructed that the partition willmaintain its shape while at the same time directing the flow of theelectrolyte.

A further object of the invention is to provide a foraminous partitionof the type described comprising a plurality of electricallynon-conducting materials.

A more specific object of the invention is to provide a foraminouspartition of the type described comprising a first foraminous tubularelectrically non-conducting material having filaments thereinoverlapping one another and running obliquely with respect to theannular electrolyzing zone and a second foraminous tubular electricallynon-conducting material concentrically arranged with re-- spect to saidfirst material.

Other objects and advantages of the invention will appear from thefollowing description in conjunction with the accompanying drawing inwhich I FIGURE 1 is an elevational sectional view of an electrolyzingcell of the type with which the invention is particularly concerned;

FIGURE 2 is an enlarged sectional view of a part of one of theelectrodes of the cell of FIGURE 1;

FIGURE 3 is a plan sectional view taken along the line 33 of FIGURE 1;

FIGURE 4 is a fragmentary view of one type of material employed inconstructing a foraminous partition as shown in FIGURES 2 and 3;

FIGURE 5 is a fragmentary view of another type of material employed inconstructing a foraminous partition as shown in FIGURES 2 and 3; and

FIGURE 6 is a view taken along the lines 66 of FIGURE 5.

In accordance with the invention a foraminous partition is providedwhich is adapted to be used within an annular electrolyzing zone of acell for electrolyzing a sacrificial anode in a liquid electrolyte andwhich comprises a tubular electrically non-conducting material havingfilaments therein overlapping one another and running obliquely withrespect to the longitudinal axis of the electrolyzing zone. Theoverlapping filaments are secured together at the points where theyoverlap. The filaments employed preferably overlap at angles of 60 andabout They are preferably extruded filaments. In the preferredstructure, there are outer and inner filaments. All of the outerfilaments run in the same direction parallel to each other and all ofthe inner filaments run parallel to each other and in a differentdirection from the outer filaments so that the spaces between them formoblong parallelograms. Where the filaments intersect or overlap, theyare secured together so as to provide a structure which is flexibletransversely but relatively rigid or substantially inflexiblelongitudinally. In other words, the tubular structure can be deflectedfrom the vertical plane but does not yield when pulled longitudinally.

It is usually preferable for the purpose of the invention to have theouter set of filaments somewhat larger in diameter than the inner set offilaments. Thus, the outer set of filaments can be, for example, 0.06inch in diameter and the inner set of filaments can be, for example,0.03 inch in diameter. A fusible or thermoplastic material is preferablyused in forming the filaments and when such a material is used, thefilaments are fused together at the points where they intersect oroverlap. A particularly suitable material from which the filaments canbe formed for the purpose of the invention is polypropylene.Polypropylene can readily be extruded to produce filaments of thedesired size which are then helically wound to produce a structure ofthe type previously described.

In practicing the invention it is also desirable in order to prolong thelife of the foraminous partition to coat the tubular electricallynon-conducting material with a resin which is substantially inert underthe conditions of cell operation. A suitable resin, for example, is anepoxy resin. A specific example of a suitable resin is the epoxy resinobtained by impregnating the tubular liner or partition with anepichlorhydrin-bis-phenol type polymer, such as, for example, a mixtureof epichlorhydrin epoxidized dihydroxydiphenyldimethylmethane having anepoxide equivalent of to 210 (Epon 828) cured with 15% by weightmonohydroxypropyldiethylenetriamine at 250 F.

It is possible to employ a tubular electrically non-conducting materialof the type previously described as the sole foraminous partition incontact with the cathode and the anode of the electrolyzing cell. Inthis case, however, the openings should be sufliciently large to permitpassage of a liquid electrolytebut small enough to permit passage of thesacrificial anode material where the latter is in particulate form, suchas, lead particles, spheres or pellets. From a practical standpoint itis better to employ a first tubular electrically non-conducting materialof the type previously described which is in direct contact with thecathode and a second tubular electrically non-conducting material havingopenings therein which is in contact with the anode particles, saidsecond material being concentrically arranged within said firstmaterial. The second material can then be readily more flexible and havesmaller openings which are preferably rectangular and this material ispreferably wound so as to form at least two layers within the firsttubular material. The second tubular material is preferably composed ofwoven filaments, such as glass fibers, or linear polyamide filaments,such as nylon. The preferred structure is one in which the first tubularelectrically non-conducting material is composed of polypropylenefilaments and the second tubular electrically non-conducting materialconcentrically disposed within the first tubular material is composed ofa woven nylon cloth. Other electrically insulating materials can beemployed in both the first and second materials, including, for example,polyethylene and a polymer of tetrafiuoroethylene. Both the first andthe second tubular materials can be impregnated or coated with a resin,preferably an epoxy resin of the type previously described. All of theseinsulating materials are inherently chemically inert.

The cell structure shown in FIGURE 1 does not in itself constitute apart of the invention but is given in order to illustrate one type ofstructure in which the invention can be employed. In the cell structureshown there is a hollow main shell 1, a second shell 2, a top endclosure member 3 and a bottom end closure member 4. The main shell 1 isprovided with an upper end plate 5 and a lower end plate 6. Each of theend plates 5 and 6 is substantially circular in cross section and isprovided with aligned openings or apertures. Electrically conductingtubes 8 which are preferably constructed of steel are Welded orotherwise secured in the apertures of the end plates 5 and 6. The numberof these tubes will vary depending upon the size of the main shell 1 andthe desired capacity of the unit. The cylindrical shell 9 is welded orotherwise secured in liquid-tight relationship to the end plates 5 and6. Likewise, the metal tubes 8 are Welded or otherwise secured inliquid-tight relationship to the same end plates. The space around themetal tubes 8 forms a chamber 10 into which a heat exchange liquid isintroduced through an inlet opening 11 and removed or recirculatedthrough outlets 12 and 13 which are provided with bafiies 14 and 15,respectively.

The second shell 2 consists of two end plates 16 and 17 having aperturestherein corresponding to the apertures in the end plates 5 and 6 of themain shell 1. A circular sheet-metal housing 18 is welded or otherwisesecured to the end plates 16 and 17 of the second shell 2 to form aliquid-tight enclosure. Short tubes 19, preferably made of steel andcorresponding in diameter to the tubes 8, are welded or otherwisesecured in liquid-tight engagement in the apertures of the plates 16 and17 of the second shell 2. Openings 20 and 21 are provided as inlet andoutlet openings to introduce and remove heat exchange fluid, if desired,or for the purpose of draining condensate from the interior of thesecond shell 2.

The top end closure 3 consists of a base plate 22 having apertures 7therein. and are aligned with the apertures in plates 5, 6, 16 and 17. Ahollow metal shell 23 is welded or otherwise secured in liquid-tightengagement to the base plate 22. At the top of this shell is an inlet 24where anode material, such as lead particles, spheres, or pellets, canbe charged and also an opening 25 where the electrolyte can beintroduced or withdrawn. A metal reinforcing band 26 is welded to theinside the shell 23.

These apertures correspond in size The top closure member 3 is assembledwith the cell by means of bolts 27 extending through bolt holes in theflanges 16 and 22. An insulating sheet 28 is placed between the endplates 16 and 22 thereby electrically insulating the end closure 3 fromthe second shell 2. The second shell 2 is similarly bolted to the mainshell 1 by means of bolts passing through holes, not shown, in the outerends of plates 5 and 17. An insulating sheet 29 is placed between theplates 5 and 17 thereby electrically insulating the second shell 2 fromthe main shell 1.1

At the bottom of the cell the end closure 4 consists of a generallyconically shaped housing 30 provided at the top with an end plate 31which is welded or otherwise secured in liquid-tight engagement to thehousing 30 and has apertures therein corresponding to the apertures inthe plates 5, 6, 16, 17 and 22. A metal grate or screen 32 is placedover the opening 33 in the bottom of the member 4 to support the anodematerial and to permit the passage of liquid electrolyte withoutpermitting the passage of the anode material. This screen or grate isheld in place by means of bolts 34 m any other suitable manner. Thearrangement is such that by removing the bolts 34 the screen or grate 32can be removed to permit cleaning of the cell and removal of all of theanode material, when necessary.

A circular plate 35 with apertures therein is placed between the endplates 6 and 31 and is insulated with electrically non-conducting sheets36 and 37. The bottom closure member 4 is assembled in liquid-tightengagement to the main shell 1 by means of bolts 38 passing throughholes in the outer edges of the plates 6, 31 and 35. The cell issupported from a supporting structure 39 which is suitably mounted toprovide a firm base.

The insulating members 28, 29, 36 and 37 all contain aperturescorresponding in size and alignment to the openings 7 and are made of asuitable electrically non-conducting material, such as, polyethylene,polypropylene or a polymer of tetrafluoroethylene (Teflon). Extensions40 and 41 are welded or otherwise secured to the end plates 5 and 6,respectively, and are connected to a negative source of potential, thatis, a source of negative direct current suitable for operation of thecell. It is desirable to employ a number of these extensions secured tothe end plates 5 and 6 at equally spaced distances. For example, in acell of the type'described in the drawings, eight such extensions arepreferred.

The end closure 4 contains downwardly extending triangularly shapedmembers 42 which are welded or otherwise connected to the shell 30 andserve as connections to a positive source of electrical potential.Again, it is preferable to employ a plurality of these anode connectionsequally spaced from one another and in a cell of the type described,eight such extensions would be used.

As shown in FIGURES 2 and 3 each of the tubular electrodes Scomprises anouter metal tube 43, a foraminous partition generally indicated at 44and an anode material, for example, spherical lead particles, generallyindicated at 45. In FIGURE 2 the tubular electrodes are shown withoutthe anode material.

The foraminous partition 44 consists of a tubular electricallynon-conducting material 46, the outer surface of which is in directcontact with the inner surface of the metal tube 43 and a second tubularelectrically nonconducting material 47 which is disposed concentricallyWithin the tubular material 46, the inner surface of which is in contactwith anode material 45.

The inner tubular material 47 is'preferably a woven filamentary materialcomposed of glass filaments, polyamide (nylon) filaments orpolypropylene filaments and the structure is such that the openings 48are small enough to prevent the passage of the anode material but largeenough to permit the flow of a liquid electrolyte. In a preferredembodiment as shown in the drawings, a double wrap of nylon cloth isused having a 92 x 92 thread count and a 1/1 plain weave. The threads inthis case are made from nylon monofilaments and the double wrap is soarranged that the ends Wrapped together overlap each other by aboutone-half inch.

The foraminous tubular member 46 has openings 49 therein which can bedescribed as oblong parallelograms.

The actite angles of the parallelograms extend in a generally verticaldirection. In the structure shown in FIG- URE 6, there is an outer setof filaments 50 extending at an angle to the vertical and an inner setof filaments 51 which also extend at an angle to the vertical but in theopposite direction. Thus, the outer set of filaments overlaps the innerset of filaments and they are secured together at their points ofintersection. It is preferable to form both sets of filaments of athermoplastic material, for example, polypropylene, and to fuse themtogether at the points where they overlap or intersect. This produces anexceptionally strong structure which is flexible transversely butsubstantially inflexible in a vertical direction.

The foraminous partition 44 is placed inside of each of the tubularelectrodes 8 by first assembling it on a short flanged tube 52 as shownin FIGURE 2. This tube 52 has a tubular portion 53 and a flanged portion54. The foraminous member 47 is placed around the short tubular portion53 and the foraminous member 46 is placed around the foraminous member47 so that they are concentrically arranged and the tops of both theforaminous members 46 and 47 are in contact with the lower surface ofthe flange 54. They are then clamped in place by means of a clampingring 55. If desired, the tube 53 can be slightly enlarged or flared at56 in order to insure that the clamping ring cannot possibly slip downbelow the lower end of tube 53. The flanged tube 52 with the foraminouspartition 44 mounted thereon is then inserted in the tubular electrode 8so that the flange 54 sits in a recess 57 in the upper part of plate 16.The tubular member 46 is then in contact with the inner surface of theshell 43. More specifically, the outer filaments 50 of the tubularmember 46 are in contact with the inner surface of the shell 43. Theinner filaments 51 are in contact with the second tubular member 47which consists of a double Wrap of a woven fabric made from nylon orother suitable material. The latter in turn is in contact with the anodematerial which may consist, for example, of lead pellets, spheres, orparticles. In a like manner, other foraminous partitions are suspendedor supported in other tubes 8 within the cell. Each of these foraminouspartitions extends from the plate 16 to the bottom of the plate 6 andcan, if desired, extend into the lower end closure member 4.

Since the foraminous partition is constructed entirely of electricallyinsulating materials, it is not necessary to take precautions to keepthe partition from going beyond the insulating element 37. On the otherhand, if the partition were constructed even in part of electricallyconducting materials in contact with the cathode any slipping or saggingof the partition might produce a short circuit. The structure of theforaminous partition provided in accordance with the invention is suchthat it offers the maximum resistance to stress or pressure imparted toit by the anode material. Furthermore, the arrangement of the filaments50 and 51 in the part of the partition adjacent the cathode provides aseries of channels or passageways for electrolyte whereby theelectrolyte is circulated in contact with both the anode and thecathode. Thus, the foraminous partition is so constructed that ti willmaintain its shape while at the same time directing the flow of theelectrolyte.

The invention is hereby claimed as follows:

1. In an electrolytic cell having a first electrode in the form of atube and a second electrode in the form of particles, and a foraminouspartition in contact with the inner surface of said first electrode andthe outer boundaries of said particles, said foraminous partitioncomprising a tubular, chemically inert, electrically non-conductivematerial having openings therein formed from filaments overlapping oneanother, said filaments running obliquely with respect to thelongitudinal axis of said first electrode, and secured together at thepoints where they overlap, and said tubular forarninous partition beingflexible transversely but substantially inflexible longitudinally. V

2. In an electrolytic cell as claimed in claim 1,2 fo raminous partitionin which said filaments overlap at angles of about 60 and about 3. In anelectrolytic cell as claimed in claim 1, a fo= raminous partition inwhich said overlapping filaments are fused together.

4. In an electrolytic cell as claimed in claim 1, a fo= raminouspartition in which there is an outer set of filaments and an inner setof filaments, the filaments in the outer set being of larger diameterthan those in the inner set.

5. In an electrolytic cell as claimed in claim 1, a 0- raminouspartition in which said filaments are resin coated.

6. In an electrolytic cell as claimed in claim 1, a foraminous partitionin which said filaments are coated with an epoxy resin.

7. In an electrolytic cell as claimed in claim 1, a 0- raminouspartition in which said filaments are formed of polypropylene.

8. In an electrolytic cell having a first electrode in the form of atube and a second electrode in the form of particles, and a foraminouspartition in contact with the inner surface of said first electrode andthe outer boundaries of said particles, said foraminous partitioncomprising a first tubular, chemically inert, electrically nonconductingmaterial having openings therein in the shape of an oblongparallelogram, said openings being formed from filaments intersectingeach other, running obliquely with respect to the annular electrolyzingzone, and secured together at their points of intersection, and a secondtubular electrically non-conducting material having openings therein,said second material being concentrically arranged with respect to saidfirst material.

9. In an electrolytic cell as claimed in claim 8, a foraminous partitionin which said second material comprises rectangular openings of smallersize than the openings in said first material, said openings in saidsecond material being sufiiciently large to permit passage of a liquidelectrolyte but small enough to prevent passage of sacrificial anodeparticles.

10. In an electrolytic cell as claimed in claim 8, a foraminouspartition in which said second material is wound to form a doublethickness of said material.

11. In an electrolytic cell as claimed in claim 8, a foraminouspartition in which said second material is a woven fabric made fromlinear polyamdie filaments.

12. In an electrolytic cell as claimed in claim 8, a foraminouspartition in which said first material consists of helically woundpolypropylene filaments and said second material consists of a fabricwoven from linear polyamide filaments.

References Cited by the Examiner UNITED STATES PATENTS 2,411,638 11/1946 Santord et al 204229 3,147,150 9/1964 Mendelsohn et al. 1361433,180,810 4/1965 Pearce et al. 20459 FOREIGN PATENTS 63 8,649 3/ 1962Canada.

20,542 10/ 1895 Great Britain.

JOHN S. MACK, Primary Examiner.

R. MIHALEK, Assistant Examiner. l

1. IN AN ELECTROLYTIC CELL HAVING A FIRST ELECTRODE IN THE FORM OF ATUBE AND A SECOND ELECTRODE IN THE FORM OF PARTICLES, AND A FORAMINOUSPARTITION IN CONTACT WITH THE INNER SURFACE OF SAID FIRST ELECTRODE ANDTHE OUTER BOUNDARIES OF SAID PARTICLES, SAID FORAMINOUS PARTITIONCOMPRISING A TUBULAR, CHEMICALLY INERT, ELECTRICALLY NON-CONDUCTIVEMATERIAL HAVING OPENINGS THEREIN FORMED FROM FILAMENTS OVERLAPPING ONEANOTHER, SAID FILAMENTS RUNNING OBLIQUELY WITH RESPECT TO THELONGITUDINAL AXIS OF